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what tube for a preamp

Discussion in 'Amps and Cabs [BG]' started by xcental34x, Apr 15, 2003.

  1. xcental34x


    Feb 28, 2003
    Memphrica, TN
    My friend has an SWR Bass 350. I recently came to find out it has a tube preamp that even he wasnt aware of. He's had it oh, for about a year. Lately the sound of his amp has become duller than what it used to be. He's playing a Stingray with a pick so its usually a nice sharp, twangy sound. I know he needs a 12ax7 tube. But what brand would you reccomend him use? I've seen Mesas, Rubies, Groove Tubes and all sorts of others. To return that snappy, sharp sound, what would he need?

  2. Try a Chinese 12at7, I find they are a nice tube, mesa uses the chinese 12at7 but with high standards. It has a nice mellow tone, and a nicer overdrive than a standard 12ax7, but less gain, so less overdrive.
  3. Hmm, Preamp tubes generally last for several years before going bad. Make sure to go through the other usual suspects such as old strings, dead batterys and bad cords etc.
  4. bollefen


    Mar 13, 2003
    can't recall where but i saw a site for stereo audiophiles with various tube characteristics.

    i had a class A tube pre-amp that was glassy bright and replced them successfully using the recommendations

  5. Groove Tubes reecently issued a 7025 (12ax7). I'm using it in my Eden Nav. Great tube!

    I've also heard good things about the EH 12ax7.
  6. seansbrew


    Oct 23, 2000
    Mesa AZ.
    I put an electro harmonix tube in my sm-500 and it gave the amp a ballsy tone I highly recomend them. I think you can find them at tubeworld.com or tubeking.com
  7. bollefen


    Mar 13, 2003
    i'm probably dating myself but grew up with tubes and am an ee.

    preamp tubes rarely need to be replaced. while tone of the tube is an issue and may be reason to change, if the tube does not suffer noise problems or microphonics it is most likely fine.

    microphonics can often be corrected with a bit of silicon on the base (not adhesive) or rubber rings made for the purpose. i wouldn't really think there is a problem with the tube. old tvs and stereo ran years and years with original preamp tubes and are harvested from old equipment today for reuse.
  8. Agreed, but it's an easy and inexpensive way to find a good/modify existing tone.
  9. Try to find a good NOS (new old stock) tube. GE, Sylvania, or RCA. Or Mullard, Telefunken, or Amperex Bugle Boy (even better). I can't say that I like any of the current production 12AX7's.
  10. fender58

    fender58 Guest

    Sep 8, 2000
    Southern California
    I am getting ready to change the pre amp tube in my Ashdown ABM-500. Has anybody else done there Ashdown. I was recomended the JJ/Telsa ECC83S and the Sovtek 12AX7LPS. I am just trying to figure out the High gain vs. Low gain relationships to the music I play which is blues/rock. I am told higher gain is better for Metal and lower gain is good for the Blues. Anybody have any knowlege? I looked at http://www.dougstubes.com/ (Doug was a big help) and at http://www.thetubestore.com/
    (Jon helped a lot too)

  11. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    "Try to find a good NOS (new old stock) tube. GE, Sylvania, or RCA. Or Mullard, Telefunken, or Amperex Bugle Boy (even better). I can't say that I like any of the current production 12AX7's."

    I agree with the above. In addition, I've found that recently manufactured tubes do not usually last very long. I would certainly try a new tube in the SWR.

    My favorite tube for the SWR preamp is the RCA 7025. They are getting hard to find, however. I have a Telefunken in my Super Redhead. Sounds great.

  12. I finally installed the Sovtek 5751 I bought a while back into my Demeter 201s and I'm impressed so far. I was experiencing my sound getting lost in the mix even after eq-ing what I could, sort of "spring ee" undefined. I had EH12ax7 that came with the pre. The 5751 gave it an all around smoother but pronounced tone across the the board especially in the lows and lower mids. I heard the term "darker", and I guess that would apply. (when I hear that I always get this image of Darth Vader..weird) I have to do what I call the true test as yet. That is, playing live wit da band. To me that is the only way to be truely happy about my sound. I can just love what I'm hearing with my gear at home, but get out on gig, that can all change real fast. I think I'm gonna like the 5751 and if so would be willing to bite the bullet for some NOS glass. I'm also getting a Demeter HBP1 in a few days to temporaily cure some major GAS pains. I'm hopeless. :D
  13. Well the 5751 did not work out. They went microphonic before long. I was warned they might.
    I'm going to find some Bugle Boys but in my research I'm finding that there are some newer versions that may not be up to the NOS snuff so to speak. I'm also interested in the Telefunken 12ax7 with the "ribbed plates" as opposed to the flat plates, NOS. Im not sure which would be the best and it seems you must have years of real experiance with tubes to REALLY know what your getting..... Comments please. :confused:

    The only true test is listening, but that can get real expensive...:meh:
  14. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    I have A/B'd smooth and ribbed plate Telefunken ECC83's and could not hear any difference although some say the smooth plate sounds better.

    NOS US and European tubes are getting scarce and expensive. You can ocasionally get Telefunkens at decent prices on Ebay. Be certain that the tube(s) have a <> diamond molded in the glass in the center of the pins. Tubes made by Telefunken all have this marking. Some tubes sold by Telefunken were manufactured by other makers and do not have that diamond.

    Feel free to email me with other questions about tubes.


  15. FretNoMore

    FretNoMore * Cooking with GAS *

    Jan 25, 2002
    The frozen north
    I was recommended by Hevos to change from the Sovtek tubes they used previously (not very reliable according to them) to Ruby Tubes (Chinese ECC83/12AX7A-C) that supposedly are of higher quality. I can't say I hear any difference in sound.
  16. bollefen


    Mar 13, 2003
    i'm surprised to hear of tubes going microphonic so fast?? are you putting the preamp right on your cabs? even so i have never had such short life. used all manner of ampegs and still have a mesa.

    do others have such problems and did you try the tube damper solution i mentioned in an earlier post.
  17. FretNoMore

    FretNoMore * Cooking with GAS *

    Jan 25, 2002
    The frozen north
    Forgive me if I'm silly, but perhaps he needs new strings instead of new tubes?
  18. Try this site for good info on current tubes available, what they are etc.

    The Tube Store

    Some companies like Groove Tubes and Ruby are just branding stuff made in China.

    There is a good review of tubes available on the site as well. Read the 12AX7 review.
  19. I'm going try some JJ ECC83S 12ax7 tubes. I ordered them as a matched pair even down to the triode. I really never heard of matching preamp tubes before so I hope I didn't get a "wolf ticket", but they were only $20.00 bucks for the pair. I read a few reviews on this valve and it's supposed to be very close to the Telefunken 12ax7 NOS. The newer "S" tube which just came out is supposed to be very very close according to the distributor (of course). At around a $100.00 each for the Telefunken's (if you can find them or Amperex Bugle Boys) that is pretty stiff to me.

    I'm hep to the TubeStore. They are pretty good to deal with, but their review on the JJ's I just bought was not to great, but...

    Actually I exaggerated the microphony on the 5751 Sovteks. There was a "ping/ring", that instantly disappeared after I changed back to the EH 12ax7 that came in my Dem 201S. I call that being microphonic. If not it was irriating. I should call and get my money back or ask for a replacement.

    Another note. I was told that Sovtek 5751 are not truely a 5751... ( I don't want to mention names etc. because I don't know who is full of it or what)
    I'm beginning to wonder who really know what the heck they a talking about. :meh:
  20. Chuck M

    Chuck M Supporting Member

    May 2, 2000
    San Antonio, Texas
    I have tried the JJ's and they are nice sounding tubes. They do not sound as good as the Telefunken's IMO. I am running a pair of JJ's in the last two sockets of my SVT IIP. The preamp has a Sylvania in the first socket and sounds great.

    Matching of tube sections is not necessary in a bass preamp. It is desirable in a audiophile Hi Fi stereo preamp.